Straight bevel gear grinding machine

ABSTRACT

The straight bevel gear grinding machine of the invention comprises a cradle mounted in the machine base and adapted to impart to the grinding wheel a generating motion, the front and rear faces of said cradle having rectangular holes, wherein guide members are accommodated, adapted for the carriage carrying the spindle with the wheel to be arranged inside the cradle. To impart to the cutting tool an oscillating motion along the tooth space of the gear being machined, the carriage is provided with a driving means mechanically associated therewith.

United States Patent 1 1 1 3,928,944

Kedrinsky et al. Dec. 30, 1975 1 STRAIGHT BEVEL GEAR GRINDING 2,620,599 12 1952 Riley 51 52 MACHINE 2,747,468 5 1956 Wildhaber.

2,860,451 11/1958 Deakin 51/56 [76] Inventors: Vasily Nlkolaevich Kedrinsky, ulitsa Vavilova 93, kv. 23; Ivan Dmitrievich Zakharov, Kavkazsky bulvar, 41, korpus l, kv. 5, both of Moscow, U.S.S.R.

22 Filed: Mar. 8, 1974 57 ABSTRACT Primary ExaminerAl Lawrence Smith Assistant Examiner-K. J. Ramsey Attorney, Agent, or Firm-Haseltine, Lake & Waters l PP 6 The straight bevel gear grinding machine of the invention comprises a cradle mounted in the machine base and adapted to impart to the grinding wheel a generat- 2 {g i 8' 51/33 5 2 ing motion, the front and rear faces of sald cradle hav- [58] Fieid w 52 R ing rectangular holes, wherein guide members are accommodated, adapted for the carriage carrying the spindle with the wheel to be arranged inside the cradle. To impart to the cutting tool an oscillating motion [56] References Clted along the tooth space of the gear being machined, the UNITED STATES PATENTS carriage is provided with a driving means mechani- 1,l67,957 1/1916 Ward 5l/32 ally associated therewith. 1,797,341 3 1931 1-1111 90/6 2,361,599 10 1944 Candee 90/6 6 Clams, 10 Draw/"1g Flgul'es 67 i I? 55 Z? US. Patent Dec. 30, 1975 Sheet 10f4 3,928,944

US. Patent Dec. 30, 1975 Sheet 3 of4 3,928,944

US. Patent Dec. 30, 1975 Sheet4 0f4 Y 3,928,944

STRAIGHT BEVEL GEAR GRINDING MACHINE The present invention relates in general to gear finishing machinery and has particular reference to ma chines for grinding straight bevel gears by the generating method with the use of abrasive disk tools.

The invention is also applicable for machining facetype clutch couplings.

The invention can be used to best advantage for machining hardened-teeth bevel gears, as well as for cutting fine-pitch bevel gears from solid blanks with the help of an abrasive wheel.

All prior-art straight bevel gear grinding machines using the generating method have abrasive tools mounted on the spindles rotated from the drive source and mounted on the grinding-wheel carriage.

Such a machine may have a roll cradle whose front face mounts the wheel carriage adapted to reciprocate along the ways provided on the cradle face. Reciprocating motion of the carriage enables the wheel to travel along the tooth space of the gear being machined. The cradle, in turn, is kinematically associated with the spindle carrying the gear being machined. In some known machines two grinding wheels are used, which are mounted on two corresponding spindles so that their axes are inclined to the cradle axis, said spindles being mounted on carriages fastened to the cradle face and are not movable along the tooth space.

The prior-art machines fail to provide a reasonably high rigidity of the cradle, since its face surface has no room enough to accommodate adequately rugged ways, which holds especially true of machines intended for grinding small gears, this being due to the fact that the cradle diameter in such machines is too small as compared with the abrasive wheel diameter. Since the machine is of low rigidity the required accuracy of machining is attainable only due to multiple grinding passes, i.e., at a low productivity of the machine.

Another disadvantage inherent in the prior-art machines is difficulty to obtain crowned teeth having a predetermined amount of crowning. When grinding is effected with two inclined disk wheels, the usual way of obtaining a crowned tooth is to impart a concave dishlike shape to the abrasive wheels. However, this calls for a very complicated design of the wheel dressing device and, besides, results in that the amount of crowning varies as the wheel gets worn, whereas the pressure angle at the tooth ends differs from its mean value.

In machines using one or two abrasive wheels adapted to reciprocate along the tooth, the crowning can be imparted to the teeth only by slight variation in the wheel travelling path. This, in turn, involves the use of an auxiliary means in the wheel carriage, adapted to move in the direction square with the aforesaid one and a complicated device making the wheel perform a variable-path motion. Besides, the wheel has to be imparted one more motion, viz., on intermittent feed motion to compensate for wear on the grinding wheel. All these factors make the wheel carriage overcomplicated, adversely affect its rigidity and hamper the protection of its mechanisms from being penetrated by abrasive dust, since all the mechanisms discussed above are located outside the cradle and close to the zone of abrasive dust formation.

Further complication of the design of a movable carriage and reducing of its rigidity is called forth in the known machines by the necessity of its being set for a required cone distance of the gear being ground. The machines of all the heretofore-known designs with the carriage mounted on the cradle, has an auxiliary slide carrying the aforesaid elements and capable of a radial setup motion with respect to the cradle axis. However, provision of such a slide not only sophisticates the carriage but also reduces the rigidity thereof.

All the heretofore-known machines having a cradlemounted movable carriage and imparted motion from a crank gear, apart from the useful force applied in the direction of the carriage movement, develop also an alternating force effective in the crosswise direction, thus causing useless additional load upon the precision ways and creating tendency towards the carriage vibrations.

It is an essential object of the present invention to provide a straight bevel gear grinding machine, wherein the arrangement of the carriage inside the cradle ensures higher rigidity of the machine as compared to the known machines of the same type.

It is another object of the present invention to provide a straight bevel gear grinding machine which ensures a possibility of grinding crowned teeth with simple means by virtue of changing the tool travel path in the course of gear-grinding process. 4

Said and other objects are accomplished in a machine for grinding straight bevel gears by the generating method using abrasive disk tools, comprising a basemounted cradle kinematically associated with the spindle carrying the gear being ground and adapted to impart a generating motion to the tool set in another spindle receiving a rotational motion from the main motion drive and mounted in the carriage in order to impart to the tool an oscillating motion along the tooth space of the gear being machined. According to the invention, the front and rear cradle faces have rectangular holes, wherein guide members are mounted to accommodate inside the cradle the carriage adapted to perform an oscillating motion along the tooth space of the gear being ground, said oscillating motion being imparted thereto from a drive means mechanically connected to the carriage.

Due to the fact that the carriage carrying the abrasive wheel, is mounted inside the cradle, only a minimum possible portion thereof with the abrasive wheel protrudes beyond the cradle, whilst the length of the carriage accommodated inside the cradle is much more than that of the protruding portion of the carriage. This imparts more rigidity to the entire structure and provides for a possibility for the grinding tool to perform a path that enables machining of a crowned-teeth gear.

According to the present invention, the guide members for arranging the carriage therein have an L-shape in cross-section and adjoin with one of their surfaces to the rear and front cradle faces, and with the other surfaces, to the top and bottom surfaces of the cradle holes, the top surfaces of the holes and the surfaces of the guide members which are adjacent thereto, have a slope towards the cradle interior to make it possible to adjust the clearance between the carriage and the guide members which in turn enable the wear on the carriage rubbing parts to be compensated for.

It is most expedient, with the carriage located inside the cradle, that the carriage end opposite to the spindle-carrying one, be shaped as a cylinder with a radius R, whose axis coincides with the axis of the spindle rotation, the surface of said cylinder being adapted to 3 sliplessly roll to-and-fro over the surface of a supporting member held in the cradle, with the result that the tool moves in the plane perpendicular to the cradle axis, while the tool effective contour moves along the tooth space of the gear being ground.

One of possible means to preclude slipping of the surfaces of the supporting member and of the carriage may be made as at least one tooth provided on the carriage and adapted to be engaged with two planes of the plate secured to the supporting member which embrace said tooth.

To provide the possibility of grinding crowned-teeth gears the surface of the supporting member over which rolls the cylindrical surface of the carriage, is made concave, whereby the tool axis during the grinding process moves along a concave path that corresponds to the curvature of a crowned tooth. By appropriately changing the supporting member, it is possible to grind gears with any reasonable amount of crowning.

In the course of machine operation the grinding wheel gets worn and is to be regularly dressed, whereby its diameter decreases, accordingly. To compensate for such wear, the wheel when being dressed, is to be shifted towards the workpiece. In the machine according to the invention, the supporting member is mounted in the separate ways arranged in the cradle at the right angle to the wheel spindle axis so as to provide a periodical travel of the spindle in the direction square with the direction of an oscillating motion performed by the wheel, as the latter gets worn.

For the machines of the type discussed herein it is essential that the carriage carrying the grinding wheel be relieved from transverse forces which are imparted thereto by the drive arrangement.

Said transverse forces add to the pressure exerted upon the guide members in which the carriage is mounted, which causes their premature and unjustified wear and affects adversely the gear grinding accuracy.

In order to relieve said forces the carriage is imparted oscillating reciprocations through a frame mounted in separate ways provided on the cradle front face square with its axis of rotation and adapted to take up said transverse forces.

When setting up the machine, one must so position the carriage that the grinding wheel would perform an oscillating motion at a definite place which depends upon the position of the toothed rim which in turn is the function of the cone distance of the gear being ground.

In one embodiment of the constructional arrangement the frame has rectilinear ways, wherein is mounted a slide adapted to be moved lengthwise the frame and held in the required position which depends upon the cone distance of the gear being ground and also provided with a slot for a slide block which has a hole into which the crankpin is fitted, which is mounted on the cradle shaft and imparted rocking motion from an external source.

As distinct from the known designs, in the proposed machine the setting of the cone distance does not constructionally complicate the carriage nor does it reduce the rigidity thereof.

As a matter of fact, in the above-discussed embodiment said setting is attained due to variation in the length of the frame assembly interconnecting the carriage with the drive arrangement for which purpose provision is made for a slide which makes the frame assembly variable in length.

In another embodiment of the present invention the length of the frame is constant which is attained due to the fact that the frame may have a slot for the slide block which is provided with a hole into which the crankpin is fitted, the latter belonging to the drive shaft which receives rotation through the telescopic shaft from an external drive mounted in a block movable along the cradle face in the direction of the frame movement and adapted to be held in the required position depending upon the cone distance of the gear being machined.

In what follows the present invention is illustrated in a detailed disclosure of a specific embodiment thereof given with reference to the accompanying drawings, wherein:

FIG. 1 is a front elevation of a straight bevel gear grinding machine, according to the invention with a portion thereof broken away to illustrate the cradle mounting particulars;

FIG. 2 is a gearing diagram of the gear grinding machine, according to the invention;

FIG. 3 is a general longitudinal-section view of the cradle, according to the invention;

FIG. 4 is a section taken on the line IVIV passing through the axis of the cradle rotation in FIG. 3;

FIG. 5 is a section taken on the line V-V square with the cradle axis in FIG. 3;

FIG. 6 is a general view of the supporting member, according to the invention;

FIG. 7 is one of the embodiments of the carriage drive, according to the invention showing the cradle front face;

FIG. 8 is another embodiment of the carriage drive, according to the invention showing the cradle front face;

FIG. 9 is a ratchet gear of the carriage drive with a partly sectional view of the hydraulic cylinder; and

FIG. 10 is a section taken on the line X-X in FIG. 9 to show the fixation of the supporting member, according to the invention.

Proposed herein is a machine for grinding straight bevel gears by the generating method using abrasive disk tools made as a grinding wheel.

Reference being now directed to the accompanying drawings, FIGS. 1 and 2 illustrate: a base 1 of the machine, wherein a cradle 2 is accommodated, carrying a tool W and performing rocking motion with respect to its horizontal axis 3 also referred to as the axis of swivel or pivot axis of the cradle 2. The cradle 2 is kinematically associated with a work spindle 4 carrying a straigh bevel gear G under machining, and imparts a generating motion to the tool W. The straight bevel gear G is held to the spindle 4 mounted rotatably about its axis 5 in a workhead 6. The workhead 6 is capable of travelling along the axis 5 on a swivel plate 7 which in turn can be swivelled on a sliding base 8 about a vertical axis 9 which intersects the axes 3 and 5 at the common point and set to the required angle. The sliding base 8 is traversable over the base 1 along the axis 3 of the cradle 2.

With the use of said setup motions, the apex of the gear G being machined can be brought into coincidence with the point of intersection of the axes 3, 5 and 9 for the workpiece to set with respect to the tool W.

During machine operation the cradle 2 rolls to-andfro about the axis 3 concordantly with the rotation of the spindle 4 of the workhead 6, this being due to the generating gear train receiving motion from an electric motor (FIG. 2) through a gearing 11, a shaft 12, generating speed change gears 13 and a bevel'gearing 14. The generating train comprises a shaftlS, bevel gears 16, a shaft 17 with a gear 18 set thereon, gears 19, 20 whose axles are so mounted on a rocker arm 21 that the pinion 20 is in constant mesh with a toothed contour 22 mounted on the face of a spur gear 23 meshing a gear 24. Further on, the gear train components are generating ratio change gears 25 and a worm gearing 26 whose worm wheel is made fast on the cradle 2. Due to such a constructional feature the cradle 2 is imparted, during machine operation, a rocking motion in strict accordance with the rotational motion of the shaft 15, wherefrom rotation is transmitted, via bevel gearings 27, 28, 29, index change gears 30 and a worm gearing 31 to the spindle 4 of the workhead 6.

At the moment as shown in FIG. 2, the working stroke of the cradle 2 is taking place, at which the gear 20 gets in mesh with a portion of the toothed contour 22 having internal toothing. On said portion the pitch circle radius r exceeds the pitch circle radius r on the portion, corresponding to the cradle return (idle) stroke, whereby the return stroke occurs much faster than the working stroke. The return stroke speed can be still more increased if the motor 10 is of the controlled type with a variable speed. Set on a shaft 32 receiving rotation from the shaft 15 via a worm gearing 33, is a cam 34 which, while over-coming the force developed by a hydraulic cylinder 36, exerts through an arm 35 to cause the sliding base 8 with the workhead 6 to move so as to withdraw the gear G being machined from the tool W for the time of the cradle 2 return stroke, whereas, upon the cradle return stroke is over, said cam lets the hydraulic cylinder 36 advance the gear G being machined again into the working position. With the afore-discussed scope of motions performed by the cradle 2, the spindle 4 and the workhead 6, indexing of the gear G being machined into a required number of teeth is carried out due to fact that the spindle 4 of the workhead 6 keeps rotating in the same direction during the return stroke of the cradle 2, whereby' the wheel will enter, during every next working stroke of the cradle 2, another tooth space of the gear G being ground, though not necessarily the adjacent one.

The tool W is set on a spindle 37 (FIG. 2) imparted rotation from a separate electric motor 38 transmitting rotation to the wheel spindle 37 through a belt drive 39 and a flexible shaft 40 (FIG. 3).

The cradle 2 of the machine as shown in FIGS. 2 to 10, is essentially a drum mounted on rollers in the housing of the base 1 and having, according to the invention, rectangular holes in its front face 2' and rear face 2" (FIG. 3).

Arranged in said holes are guide members referred to as top and bottom ones depending upon whether they are fitted to top surfaces 41 or to bottom surfaces 41' of said holes, and indicated respectively at Reference Numerals 42, 42' and 43, 43'.

The guide members 42, 42', 43, 43' are adapted for accommodating a carriage 44 inside the cradle 2, said carriage carrying the spindle 37 with the tool W, to enable the latter to perform an oscillating motion along the tooth space of the gear being ground.

The bottom guide members 43 and 43 are L-shaped and rest upon the respective front face 2 and rear face 2" of the cradle 2, being held to said faces with screws 45 and 45, respectively. The top guide members 42 and 42 are likewise L-shapedl, each of them having a flat surface sloped inwards the cradle and fitted to the respectively sloped flat surface 41 of the holes provided in each faces 2 and 2" of the cradle 2. Compensation strips 46 and 46 are interposed between the corresponding cradle face and the flat surface of the guide member. Provision of flat sloped surfaces and said strips enables, by appropriately grinding the strips, adjustment of the clearance between the sliding surfaces of the carriage and of the guide members, as well as compensating for wear of the rubbing parts in the course of machine service life.

The carriage 44 (FIGS. 3, 4, 5) is adapted to reciprocate during machine operation from the drive arrangement in order that the tool performs an oscillating motion along the tooth space of the gear being ground. In the herein-discussed embodiment of the machine, the drive is obtained from an electric motor 47 (FIG. 2) through a belt drive 48, a telescopic shaft 49, a crank 50 and a frame 51. The latter is mounted in separate antifriction ways arranged on the front face 2' of the cradle 2 square with the axis 3 thereof. The said ways comprise strips 52 and 52' (FIGS. 3 and 9) held to the face 2' of the cradle 2 by screws 53, 53' and having trapezoidal grooves for balls. The same grooves are provided in the frame 51 which is traversable along the antifriction (ball-type) ways and, while embracing the carriage 44, is capable of imparting thereto said oscillating motion either directly or through the intermediary of the device shown in FIGS. 3, 4. Said device comprises a pin 54 and a slide block 55 fitted into the slot of the carriage. Strips 56 and 56 protect the ball ways against dust penetration, while the frame 51 and an elastic guard 57 afford reliable protection to the carriage precision ways.

The carriage 44 has at its end opposite to that carrying the spindle 37 of the grinding wheel W, a cylindrical surface 44' (FIG. 4) of a radius R whose axis coincides with the axis of the spindle rotation. Said cylindrical surface 44' is in contact with a surface 58 of a supporting member 58 (FIG. 6) secured in the cradle 2, so that during machine operation, said cylindrical surface rolls sliplessly to-and-fro over the surface 58. As a result (in case of the surface 58' being flat), the axis of the tool W moves in the plane perpendicular to the axis 3 of the cradle 2, while the effective profile of the tool W moves along the tooth space of the gear G being ground.

The contact between the said surfaces 44' and 58 of the carriage 44 and of the supporting member 58 is maintained by virtue of the tension of a spring (not shown).

In order to preclude slippage of said surfaces of the carriage 44 and of the supporting member 58, made fast on the carriage 44 is a plate shaped as a tooth 59 (FIG. 4) of an imaginary gear whose axis coincides with the axis of the spindle 37 and the pitch circle is essentially a circumference with the radius R. Said tooth 59 is adapted to get engaged with two flat surfaces of a plate 60that embrace it, representing the corresponding tooth space for tooth 59 The plate 60 fixed to a block 61 to which the supporting member 58 is held by means of screws 62.

According to one of the aforestated objects of the invention, the herein-proposed machine enables an efficient machining of straight bevel gears having crowned teeth. To this end, the supporting member 58 may have its effective surface 58 (FIG. 6) concave. Thanks to this, with the carriage 44 moving, the axis of 7 the tool W moves along a concave path, and the teeth being ground are imparted a definite amount of crowning. For machining gears with the teeth having different amount of crowning it is necessary to have a number of change supporting members.

Since the grinding wheel is liable to wear during operation and its diameter is thus being decreased, the wheel should be shifted after every truing operation, towards the workpiece. In the machine under discussion this shifting is effected quite simply and efficiently by displacing the supporting member 58, whereby the entire grinding wheel carriage 44 is moved in the direction square with the direction of oscillating motion. To effect said displacement, fixed to the rear flange 2" (FIGS. 2 and 3) of the cradle 2 is a bracket 63 provided with a guiding surface 63' (FIG. 2) which in this particular embodiment of the machine is parallel to the cradle axis, wherein is slidably mounted the block 61 with the supporting member 58. The block 61 has a threaded hole whereinto a screw 64 is turned, which is mounted for rotation in a flange 65 fixed to the bracket 63 (FIGS. 2 and 9). The flange 65 has the hydraulic cylinder shown in FIG. 9, whose piston 66 carries a pawl 67 adapted to be engaged with a ratchet wheel 68. The hydraulic cylinder operates periodically, i.e., at the moment preceding to the grinding wheel dressing, and is operated by means of a pushbutton on the control panel or by virtue of an automatic control system. The grinding wheel dressing device is not the subject of the present invention; it is essentially a wheel dresser of one of the heretofore-known designs.

When the piston 66 moves, the pawl 67 causes the ratchet wheel 68 and the screw 64 to turn, whereby the block 61 with the supporting member 58 moves as described above. The number of teeth for which the ratchet wheel is turned are adjustable by varying the length of stroke of the piston 66 by means of a stop screw 69. When changing the grinding wheel, the pawl 67 is to be raised a little and the screw 64 be rotated manually in the reverse direction to return the carriage into the initial position.

When setting up the machine it is necessary to so position the carriage 44 that the grinding wheel perform an oscillating motion at a definite place which depends upon the position of the work gear rim determined by the cone distance thereof. In order to make said setup operation possible, an extension 70 (FIG. 7) of the telescopic shaft 49, carrying the crankpin 50 is rotatably mounted in a block 71 which is traversable over the face 2 of the cradle 2 in the direction of the oscillating motion of the frame 51 and can be held in the required position by screws 72, said position depending upon the cone distance of the gear being ground that is read off a scale 73.

FIG. 8 illustrates another embodiment of said setup means. In this case the shaft 70 with the crank 50 is rotatably mounted in the cradle 2, while the frame 51 has rectilinear ways 74, wherein a slide 75 is mounted, having a slot for a slide block 76 which is provided with a circular hole into which the crankpin 50 is fitted. When setting up the machine the frame 51 is traversable with respect to the slide 75, the amount of setting being read off a scale 77 and corresponding to the cone distance of the gear being ground. The slide can be held in the required position by a nut 78. With the aforesaid embodiment adopted, the shaft 49 does not necessarily be made telescopic, but can be made integral with the shaft 70.

When grinding a crowned-teeth gear, setting up the required cone distance involves, apart from the aforediscussed operations, also that the supporting member 58 be displaced into a definite position so that the vertex of the maximum convexity be found at the middle of the tooth. To ensure that said setup operation be possible, the bracket 63 is mounted on the rear flange 2" (FIG. 3) of the cradle 2 traversably along ways 79 (FIG. 9). Setting is carried out against a scale 80, while holding the bracket in the required position is made by means of screws 81 (FIGS. 9 and 10) turned into holddown strips 82. The movement of the bracket 63 is also convenient to be used when adjusting the contact pattern of the gear being ground.

The afore-described exemplary embodiment of the present invention refers predominantly to small-sized machines, wherein the size of the cradle and the components thereof is relatively small. In larger machines the motor 47 and the belt drive can be located on the cradle housing or on the cradle itself, while the wheel drive motor 37 can be located directly on the carriage 44.

Besides, in such machines the cradle can accommodate two grinding wheel carriages rather than one so that both tooth sides could be machined, each by its particular grinding wheel.

Said and other design particulars may be introduced or made in another embodiment of the machine, or modified, or else dispensed with, without departing from the essence and scope of the present invention and the specific terminology resorted to therein that will hereinafter be defined in the claims that follow.

The machine operates as follows.

Once the grinding wheel W and the gear G to be machined are set on their respective spindles and held thereto by means of any suitable clamping fixtures, the operator must depress the appropriate push-buttons on the control desk to start the electric motors 38, 47 and 10, whereby the following motions begin: rotation of the grinding wheel W effected from the electric motor 38 through the belt drive 39 and the flexible shaft 40; an oscillating motion of the carriage 44 carrying the grinding wheel W imparted from the electric motor 47 via the belt drive 48, the telescopic shaft 49, the crankshaft 70, the crankpin 50 and the frame 51; at last the motor 10 starts and the generating train begins to operate, receiving motion from the motor 10 which imparts rotation through the gearing 11 to the shaft 12, from whence rotation is transmitted via the change gears 13 set up for the required tooth grinding cycle duration in seconds per tooth, to the shaft 15, wherefrom rotation is further imparted, via the gearings 16, I7, 18 and 19, to the pinion 20, which rotates in constant direction and, upon meshing the toothed contour 22, causes the spur gear 23 to rotate to-and-fro. The motion is then imparted to the cradle 2 through the gears 23-24, the change gears 25 and the worm gearing 26.

As a result, when the pinion 20 is being meshed with a portion of the toothed contour having the radius r,, the cradle working stroke occurs, while with said pinion being meshed with the portion having the radius r the cradle rapid return stroke takes place.

The shaft 15 imparts rotation also to the workhead spindle 4 via a train incorporating the gearings 27, 28, 29, the index change gears 30 and the worm gearing 31. At the same time rotation is transmitted to the shaft 32 via the wormv gearing 33. The number of teeth of the gears interconnecting the shaft 32 with the shaft of the 9 crown gear 23, are so selected that a complete revolution of the shaft 32 occurs per cradle complete working and return stroke or, in other words, per tooth grinding cycle.

The cam 34 set on the shaft 32 is adapted, while acting through the arm 35 to overcome the counteraction force exerted by the hydraulic cylinder 36, so withdraws the sliding base 8 that the workpiece is retracted from the grinding wheel before the cradle starts performing its return idle stroke, whereas at the beginning of the working stroke thereof the cam lets the hydraulic cylinder 36 return the sliding base 8 into the working position.

The change gears 25 are selected to suit the generating ratio, i.e., the ratio between the turning of the workhead spindle 4 and of the cradle 2 during the working stroke of the latter.

The index change gears 31 are selected to suit the number of teeth of the gear being ground so that in the course of a complete working and return stroke of the cradle 2 the spindle 4i turns to an angle corresponding to a whole number of teeth having no common multiplication factors with the entire number of teeth of the gear being machined. Thanks to this, during every next cradle working stroke the grinding wheel will enter a next, though not necessarily the adjacent tooth space of the gear being ground.

With the motor 47 running, the frame 51 imparts, as it has been stated above, an oscillating motion to the carriage 44 Said motion as a matter of fact is a rolling motion of the carriage over the surface 58' of the supporting member 58. Since the surface of the carriage 44 that is in contact with the surface 58, is a cylindrical one described at the radius R relative to the axis of the grinding wheel rotation, said axis (in case of the surface 58 being flat) moves in the plane perpendicular to the cradle axis. When the surface 58 of the member 58 is made concave the character of the motion performed by the spindle axis changes, i.e., said axis will move along a concave path, and the teeth being ground will assume a crowned shape. To provide a possibility of grinding crowned-teeth gears with various amount of crowning the member 58 is made changeable.

The grinding wheel due to wear loses its true geometrical shape and, therefore, needs periodical dressing which is carried out, as it has been pointed out above, with the use of a wheel dressing device which is left beyond the scope of the present invention. Wheel truing reduces its diameter, on which account the wheel is to be shifted forwards lest the position of the grinding wheel active surface with respect to the workpiece should be changed, which can be attained, with the herein-discussed embodiment of the machine, by advancing the whole carriage 44 towards the workpiece. Upon depressing the appropriate push-button on the control desk or in response to a command signal from the counter of the cradle rockings equal to the number of revolutions of the shaft 32, the spool valve of the hydraulic system is put into operation to let the pressure fluid flow into the hydraulic cylinder which is made as a bore in the flange 65 (FIG. 2), with the result that the piston 66 starts travelling from right to left and its pawl 67 causes the ratchet wheel 68 to turn through a definite number of teeth depending upon the length of stroke of the piston 66 which is set by the adjustable stop screw 69. The ratchet wheel 68 rotates the lead screw 64, thus causing the block 61 with the supporting member 58 to move parallel to the cradle axis 3. As

soon as the grinding wheel gets dead-worn, it must be changed for which purpose the carriage 44 is to be retracted into the initial position by manually rotating the lead screw 64, with the pawl 67 raised a little.

When setting up the machine, the carriage 44 must be set so as to suit the cone distance of the gear being ground. To this end, the nuts of the screws 72 must be undone, whereupon the block 71 together with the crankshaft and the frame 51, must be traversed directly by hand or through the agency of any arrangement suitable for the purpose, into the required position set against the scale 73. This done, the nuts of the screws 72 are to be retightened. When grinding uncrowned-tooth gears (with the surface 58' of the supporting member 58 being flat) the setup procedure boils down to the above operation, whereas in case of crowned-tooth gears (when the surface 58' is a concave one) it is necessary to so displace the member 58 that the midpoint of its concave surface be positioned oppositely to the middle of the work gear tooth. To perform the appropriate setup operation, it is necessary to undo the screws 81 and shift the bracket 63 along the ways 79 into the required position depending upon the cone distance of the gear being ground which is set against the scale 80. When the bracket 63 is displaced from said position, the contact pattern of the gear teeth being ground will be displaced accordingly lengthwise the tooth; therefore such a displacement of the bracket 63 can be made use of for lengthwise adjusting of the tooth bearing contact of the bevel gear pairs being ground.

What is claimed is:

l. A straight bevel gear grinding machine comprising a rotatable cradle carrying a tool means mounted for oscillating motion inside said cradle between guide means secured in a rectangular hole provided in the cradle body; a base; a wheel rotation drive; a spindle carrying a disk tool and receiving rotation from said drive; another spindle carrying the gear being machined and mounted on said base and being kinematically associated with said cradle; said tool means comprising a carriage carrying said spindle with said disk tool inside said cradle and capable of oscillating motion; drive means mechanically connected to said carriage to impart to the latter oscillating motion lengthwise the tooth space of the gear being machined; said guide means comprising guide members mounted in said rectangular hole of said cradle for accommodating said carriage inside said cradle, said guide members being L-shaped in cross-section, one of the surfaces of said guide members being fitted to the cradle rear and front faces, while the other surfaces thereof are fitted to the corresponding surfaces of the cradle holes so that the top surfaces of the holes and the surfaces of the guide members fitted thereto have a slope towards the cradle interior to enable adjustment of the clearance between the carriage and the guide members.

2. A straight bevel gear grinding machine comprising a rotatable cradle carrying a tool means mounted for oscillating motion inside said cradle between guide means secured in a rectangular hole provided in the cradle body; a base; a wheel rotation drive; a-spindle carrying a disk tool and receiving rotation from said drive; another spindle carrying the gear being machined and mounted on said base and being kinematically associated with said cradle; said tool means comprising a carriage carrying said spindle with said disk tool inside said cradle and capable of oscillating motion; drive means mechanically connected to said carriage to impart to the latter oscillating motion lengthwise the tooth space of the gear being machined; said guide means comprising guide members mounted in said rectangular hole of said cradle for accommodating said carriage inside said cradle, said carriage having at its end opposite to the spindle-carrying one, a cylindrical surface with a radius R, the axis of said cylindrical surface coinciding with the axis of the spindle rotation, said cylindrical surface being adapted to sliplessly roll to-and-fro over the surface of a supporting member held in the cradle, whereby the tool axis moves in a plane perpendicular to an axis of rotation of said cradle, the tool effective contour moving along the tooth space of the gear being ground.

3. A straight bevel gear grinding machine comprising a rotatable cradle carrying a tool carriage mounted for oscillating motion inside said cradle between guide members secured in a rectangular hole in the cradle body, a spindle carrying a disk tool mounted for rotation in said carriage, drive means to impart to the carriage said oscillating motion lengthwise the tooth space of the gear being machined, a base, a tool rotation drive, a work spindle carrying the gear being machined and mounted on the base and being kinematically associated with said cradle, said carriage having at its end opposite to the spindle-carrying one, a cylindrical surface with a radius R, the axis of said cylindrical surface coinciding with the axis of the spindle rotation, said cylindrical surface being adapted to sliplessly roll toand-fro over the surface of a supporting member held in the cradle, whereby the tool axis moves in a plane perpendicular to an axis of rotation of said cradle, the tool effective contour moving along the tooth space of the gear being ground.

4. A machine as claimed in claim 2, wherein said carriage is provided with at least one tooth adapted to be engaged with the planes of said supporting members embracing said tooth, for precluding slippage of the surfaces of the supporting member and of the carriage.

5. A machine as claimed in claim 2, wherein the surface of said supporting member is concave to move the grinding tool during the grinding process along a concave path corresponding to the amount of crowning of a crowned tooth, the carriage cylindrical surface rolling over said supporting member and being in contact therewith.

6. A machine as claimed in claim 2, wherein said supporting member is mounted in separate ways arranged in the cradle square with the wheel spindle axis for periodically moving the carriage in the direction square with the direction of the tool oscillating motion to compensate for tool wear. 

1. A straight bevel gear grinding machine comprising a rotatable cradle carrying a tool means mounted for oscillating motion inside said cradle between guide means secured in a rectangular hole provided in the cradle body; a base; a wheel rotation drive; a spindle carrying a disk tool and receiving rotation from said drive; another spindle carrying the gear being machined and mounted on said base and being kinematically associated with said cradle; said tool means comprising a carriage carrying said spindle with said disk tool inside said cradle and capable of oscillating motion; drive means mechanically connected to said carriage to impart to the latter oscillating motion lengthwise the tooth space of the gear being machined; said guide means comprising guide members mounted in said rectangular hole of said cradle for accommodating said carriage inside said cradle, said guide members being L-shaped in cross-section, one of the surfaces of said guide members being fitted to the cradle rear and front faces, while the other surfaces thereof are fitted to the corresponding surfaces of the cradle holes so that the top surfaces of the holes and the surfaces of the guide members fitted thereto have a slope towards the cradle interior to enable adjustment of the clearance between the carriage and the guide members.
 2. A straight bevel gear grinding machine comprising a rotatable cradle carrying a tool means mounted for oscillating motion inside said cradle between guide meanS secured in a rectangular hole provided in the cradle body; a base; a wheel rotation drive; a spindle carrying a disk tool and receiving rotation from said drive; another spindle carrying the gear being machined and mounted on said base and being kinematically associated with said cradle; said tool means comprising a carriage carrying said spindle with said disk tool inside said cradle and capable of oscillating motion; drive means mechanically connected to said carriage to impart to the latter oscillating motion lengthwise the tooth space of the gear being machined; said guide means comprising guide members mounted in said rectangular hole of said cradle for accommodating said carriage inside said cradle, said carriage having at its end opposite to the spindle-carrying one, a cylindrical surface with a radius R, the axis of said cylindrical surface coinciding with the axis of the spindle rotation, said cylindrical surface being adapted to sliplessly roll to-and-fro over the surface of a supporting member held in the cradle, whereby the tool axis moves in a plane perpendicular to an axis of rotation of said cradle, the tool effective contour moving along the tooth space of the gear being ground.
 3. A straight bevel gear grinding machine comprising a rotatable cradle carrying a tool carriage mounted for oscillating motion inside said cradle between guide members secured in a rectangular hole in the cradle body, a spindle carrying a disk tool mounted for rotation in said carriage, drive means to impart to the carriage said oscillating motion lengthwise the tooth space of the gear being machined, a base, a tool rotation drive, a work spindle carrying the gear being machined and mounted on the base and being kinematically associated with said cradle, said carriage having at its end opposite to the spindle-carrying one, a cylindrical surface with a radius R, the axis of said cylindrical surface coinciding with the axis of the spindle rotation, said cylindrical surface being adapted to sliplessly roll to-and-fro over the surface of a supporting member held in the cradle, whereby the tool axis moves in a plane perpendicular to an axis of rotation of said cradle, the tool effective contour moving along the tooth space of the gear being ground.
 4. A machine as claimed in claim 2, wherein said carriage is provided with at least one tooth adapted to be engaged with the planes of said supporting members embracing said tooth, for precluding slippage of the surfaces of the supporting member and of the carriage.
 5. A machine as claimed in claim 2, wherein the surface of said supporting member is concave to move the grinding tool during the grinding process along a concave path corresponding to the amount of crowning of a crowned tooth, the carriage cylindrical surface rolling over said supporting member and being in contact therewith.
 6. A machine as claimed in claim 2, wherein said supporting member is mounted in separate ways arranged in the cradle square with the wheel spindle axis for periodically moving the carriage in the direction square with the direction of the tool oscillating motion to compensate for tool wear. 